“We were a little surprised at the numbers,” said Darrell Luzzo, senior vice president for education at JA Worldwide, headquartered in Colorado Springs, Colo. “Having a credit card is not necessarily a terrible thing, so long as they’re being educated about the appropriate financial principles.”

But while 82 percent of the teen users said they paid their bills in full every month, 18 percent said they carried balances over — a practice that has gotten many parents in trouble.

Financial experts are concerned about the growing use of credit cards by teens, even though the cards generally must be co-signed by parents if a child is under 18.

“I personally think that 13 to 14 is too young,” said Laura Levine, executive director of the JumpStart Coalition for Personal Financial Literacy, a nonprofit educational group based in Washington, D.C. “It really depends on the individual kids. … Kids mature at different rates, so I don’t think there’s a single, magic age.”

The key, Levine said, is the involvement of parents in teaching children how to use both credit and debit cards — and in monitoring their children’s use of plastic.

“You don’t give a child a musical instrument and say, ‘Plunk around on this for a while and see if you can learn to play,’ ” she said. “The act of giving kids a credit card or a debit card isn’t going to give them good money-management habits. There has to be teaching and practicing.”

Levine suggests parents who do get cards for their children sit down and go over their monthly statements, talking about subjects like interest rates, the importance of paying on time and spending habits.

That lets them learn from their mistakes while they’re still at home, not “when they’re 18 and off to college or work and they’re eligible for their own cards anyway.”

That’s what prompted Lorene Kimble of Corning, N.Y., to help get her 16-year-old daughter Heather a debit card last summer, along with both a checking and a savings account. Kimble said her goal was to teach Heather how to better manage her money, including income from an after-school job at McDonald’s.

“We sat down and talked about putting money into savings every week, about shopping with a debit card,” Kimble said. “She sees us doing it, and she’s comfortable with it.”